1. Field of the Invention
The present invention relates to electrical machines in general and, in particular, to plates that support printed circuit cards to be plugged into connectors in the machine.
2. Prior Art
The current trend in the electronics industry is to reduce the cost of boxes such as Personal Computers (PC) and other electronic devices. The total cost of a product includes both the initial purchase price and the cost for servicing and maintaining the product. It is well known that the low cost quality products stand the best chance of being successful.
One way to reduce product cost is to modularize the product. Further cost reduction can be achieved if the product is built to a standard specification. Several specifications have been promulgated for different sectors of the electronic industry. The benefit of the specification is that sub-assemblies can be purchased from different manufactures and used in a pre-existing machine or assembled into a new one.
The modularization used in the electronic industry usually requires a unit (hereinafter called a box) be modularized into sub-assemblies of a housing and circuit cards or circuit board assemblies to be mounted in the housing. The sub-assembly usually includes a frame (for mounting in the housing) and the circuit card or circuit board that the frame holds.
U.S. Pat. No. 3,775,643 describes a card support assembly for plugged-in PC cards. Different card support assemblies are required for different size PC cards. In addition, the mounting plate to which the card support assembly is attached also has to be changed to accommodate changes in the card support assembly.
Probably the foremost drawback with the card support assembly is that it can only support one type of PC card. Consequently, it violates one of the cardinal principles of low-cost manufacturing. The cardinal principle is re-useability of sub-assemblies. The advantages (including reduced cost, etc.) associated with re-useability of sub-assemblies are also well known and they will not be repeated here.
U.S. Pat. No. 5,432,682 describes a card support assembly (consisting of a mounting bracket and card bracket holder) for mounting variable length AT style cards in a computer housing. The orientation of the card is such that the card edge connector (during insertion) is perpendicular to the connector in which it is to be inserted. Stated another way, the direction of insertion into the housing is perpendicular to the direction of insertion in the connector. Even though the design of this card support assembly is a step in the right direction in that it handles different size cards, it suffers, among other things, from the infirmity of its inability to insert circuit cards in which the direction of insertion in the housing is different from the direction of insertion in the in house connector.
U.S. Pat. No. 5,490,038 describes a mounting plate for mounting different size motherboard to a chassis. This is a limited use structure only suited for the disclosed use.
In view of the above limitations, there is a need for a more versatile structure for mounting circuit cards or boards in their respective housings.